Magnetic coupling device



H. G. NEWBOULT MAGNETIC COUPLING DEVICE Nov. 29, 1955 2 Sheets-Sheet 1Filed June 29, 1951 Attorney Nov. 29, 1955 H. G. NEWBOULT MAGNETICCOUPLING DEVICE 2 Sheets-Sheet 2 Filed June 29, 1951 Attorney UnitedStates Patent MAGNETIC COUPLING DEVICE Henry Grattan Newboult, Slough,England, assignor to Ronald Trist & Co. Limited, Slough, EnglandApplication June 29, 1951, Serial No. 234,274

Claims priority, application Great Britain June 30, 1950 7 Claims. (Cl.20087) Magnetic coupling devices can be used with advantage in thecontrol of steam boilers and other containers of liquid because onemagnet can be mounted on one side of a wall of a non-magnetic containerconnected to the steam and water spaces of the boiler or the like andanother can be mounted outside the wall. If the first magnet isconnected to a float or the equivalent so that it is moved (usually byrocking about a horizontal axis), the second magnet will also be moved,either with snap action as a result of magnetic repulsion or in stepwith the first magnet as a result of magnetic attraction. To make themost efiicient use of the available magnetic forces the gap between thetwo magnets should be as small as possible, and so the outer or drivenmagnet is commonly mounted in a casing fixed to the wall of the liquidcontainer in which the inner or driving magnet is mounted. Now it thecontainer wall is hot, and particularly if the device is used in thecontrol of. a high-pressure steam boiler, the heat is conducted to thecasing of the driven magnet, which often contains a heatsensitive deviceoperated by the driven magnet. For instance, if this casing encloses anelectricswitch actuated by the driven magnet the contact elements of theswitch, and some kinds of electrical insulation, may be damaged ordestroyed by the high temperature, and if the casing encloses a valvecontrolling, say, the flow of compressed air to some device orinstrument, the lubricant necessarily present in the valve may likewisebe adversely affected.

If the container within which the driving magnet is mounted is at a verylow temperature, the conductance of heat away from the driven magnet mayalso be deleterious by producing condensation on the contacts of aswitch operated by the driving magnet or by damaging the oil of alubricated valve so operated. Again, in some installations it may benecessary for physical reasons to space the driven magnet and the deviceit operates away from the container wall.

It is an object of this invention to provide a magnetic coupling devicewhich can be used in conjunction with a hot or cold wall without risk ofdamage to any device operated thereby.

It is another object of this invention to provide an improvedconstruction of coupling device comprising a plurality of magneticmembers.

A further object of the invention is to construct a device capable oftransmitting energy magnetically at a distance.

With these and other objects in view a device according to thisinvention includes not only driving and driven magnetic members but alsoone or more relay magnetic members interposed between the driving anddriven members in such a way that the driving magnet acts on and moves arelay magnetic member, which in turn acts on and moves the driven magnetor, if there is more than one relay member, the next relay magneticmember and so on until the last relay member acts on and moves thedriving magnet. Since there is some loss of 2,725,439 Patented Nov. 29,1955 power at each air gap, it is preferred to employ simply one relaymember.

I prefer to use a device comprising three bar magnets mounted end toend, though each such magnet may be composite in that it consists of twoor more magnets placed end to end in contact with one another andmounted to rock as a unit.

The preferred construction according to the invention will now bedescribed by way of example with reference to the accompanying drawingsin which Figure l is a plan of the device, and Figure 2 is a side viewof it, mainly in section on the line 11-11 in Figure l.

The device shown serves to control an electric switch 1 in accordancewith the rise and fall of a float 2 inside a container 3 in the form or"a chamber connected to the steam and water spaces of a boiler. Thedevice includes a fitting 4 which is let into a hole in and bolted to awall 5 of the chamber 3, so as to make a fluid-tight joint with the edgeof the hole. The fitting 4 carries two arms 6 extending into the chamber3 and carrying a pin 7 which constitutes a horizontal pivot for thefloat 2. The float has a tail 3 in which a driving bar magnet 9 ishoused so that one pole of this magnet moves in an are close to theinner wall of the fitting i.

The switch 1 is mounted in a casing ltd which also contains a driven barmagnet 11 carried by a housing 12 which is mounted on pivot pins 13.When the magnet rocks, one end of the magnet 11 moves in a recess 14 inthe casing 10, the end positions of the magnet being determined by thesides of the recess, and two blade contacts 15 make and break contacts16 and 17 forming part of the switch. The casing ill is secured by tierods 18 to the fitting 4, and it has a forked extension 19 carrying apin 20. This pin serves as a pivot for a third bar magnet 21, one end ofwhich rocks in a recess 22 in the fitting 4 between end positionsdetermined by the sides of the recess and the other end of which rocksclose to the wall of the recess 14.

The magnet 21 is composite, consisting of two bar magnets end to endwith a short soft-iron cylinder 23 between them, all surrounded by asleeve 2 The pin 20 actually passes through the soft-iron 23, thusavoiding the need for piercing the magnet. In addition, this arrangementlengthens the magnet 21 and so leads to the driven magnet being furtheraway from the hot wall.

The provision of the relay magnet 21 eliminates all risk of damage byheat from the hot wall to any heatsensitive device operated by thedriven magnet ii.

The polar arrangement of the magnets is such that the third magnet 21 ismoved by magnetic attraction and the driven magnet 11 by magneticrepulsion. The reason is that if, as is most convenient, the threemagnets are of substantially the same magnetic power the torque exertedby the driving magnet 9 on the third magnet 22 should be greater thanthe counteracting torque produced by the driven magnet 11, and thereforethe distance be tween the re-acting poles should be smaller at thedriving-magnet end than at the driven-magnet end of the magnet 21. Ifthe magnet 21 is attracted by the driving magnet, the adjacent poles ofthe two magnets will always be as close together as the structuralfeatures of the device and container wall will permit, whereas at theother end of the magnet 21 the distance between the adjacent poles willbe larger until the critical position is reached at which the drivenmagnet moves with snap action. Other polar arrangements may be used,however, provided that the driven magnet will always respond to themovements of the driving magnet.

The invention is not limited to the use of magnets as described aboveand shown. The essential advantage of reducing the action of heat fromthe hot wall on the driven magnet 11 can be obtained if instead of usinga permanent magnet 21 a bar of magnetic material is used. Moreover, inan arrangement of the kind shown with the relay magnet 21 a permanentmagnet, either or both of the driving and driven magnets may be made ofmagnetic material without being permanent magnets.

Yet again, other arrangements may be used. For instance, the drivingmagnet may rise and fall in a verti cal path, causing the relay magneteither to rock, as in the arrangement illustrated, or to slide in ahorizontal path towards and away from the vertical path in accord ancewith the proximity of the one or other pole of the driving magnet to theend of the third magnet close to the vertical path.

Moreover, bar magnets arranged end to end need not be in a straightline. For instance, a relay magnet may be arranged in the Wayillustrated in relation to a driving magnet but the driven magnet may bemounted to reel; about a horizontal axis at 90 to that illustrated.

I claim:

1. in a magnetic coupling device for transmitting motion from a heatedlocation to a second location Without any accompanying transfer of heat,a first magnetic member mounted for rocking motion, a second magneticmember also mounted for rocking motion spaced from said first member byan air gap and magnetically coupled to said first magnetic member, and athird magnetic member also mounted for rocking motion spaced from saidsecond member by an air gap and magnetically coupled to said secondmagnetic member, said second member responding to movements of saidfirst member by way of said first magnetic couple and said third memberresponding to movements of said second member by way of said secondmagnetic couple, said third member being effectively isolated by meansof an intervening air space from the heat emanating from said heatedlocation.

2. in a magnetic coupling device of the kind in which a magnetic membermounted outside a wall of a container which is heated in use is drivenas a result of magnetic action by a driving magnetic member mountedinside the container wall, the improvement comprising a movable magneticrelay member mounted outside the container wall and interposed andmagnetically coupled between the other two members with air gaps formedbetween the relay member and the other two members so that the drivenmember is spaced away from the hot wall and thermally isolated therefromby means of an intervening air gap.

3. In a magnetic coupling device comprising a driving magnet mountedinside and a driven magnet mounted outside a wall of a container whichis heated in use and heat-sensitive device operated by the drivenmagnet. the improvement comprising a relay magnet mounted outside thecontainer wall between the driving and driven magnets with air gapsformed between the relay magnet and the driving and driven magnetsrespectively and the relay magnet forming magnetic couplings with saiddriving and driven magnets so that the relay magnet is moved by thedriving magnet, as a result of magnetic coupling, and in turn the drivenmagnet is moved by the relay magnet as a result of magnetic coupling,whereby said driven magnet is effectively thermally isolated from saidheated container.

4. A device according to claim 3 in which all the magnets are barmagnets arranged end to end and mounted to rock about parallel axestransverse to the bars; said relay magnet and said driven magnet beingseparated by an air space.

5. A device according claim 4 in which the driven magnet is mounted in acasing secured to but spaced away from the container wall and the relaymagnet is mounted in an extension of this casing; an electric switch insaid casing operated by said driven magnet; said electric switch beingthermally isolated from said heated container Wall by virtue of the airspace therebetween.

6. In a magnetic coupling device, three bar magnets arranged end to endeach for rocking motion about an axis transverse to the length of thebar, the adjacent poles of the first and second of said magnets spacedby an air gap and attracting one another magnetically to form a firstmagnetic couple and the adjacent poles of said second and third magnetsspaced by an air gap and repelling one another magnetically to form asecond magnetic couple.

7. In a magnetic coupling device in which a driving magnet is locatedinside a container that is heated in use; a driven magnet, and anelectric switch operated thereby, said driven magnet and said electricswitch being located in a casing remote from said container, so as to bethermally isolated therefrom; a relay magnet, operatively locatedbetween said driving magnet and said driven magnet so as to provide ameans for transmitting motion therebetween said relay magnet beingseparated from said driving and driven magnets by first and second airgaps respectively, whereby said electric switch is operated as a resultof the motion of said driving magnet, while being protected from theheat emanating from said heated container.

References Cited in the file of this patent UNITED STATES PATENTS246,718 Cable Sept. 6, 1881 2,012,153 Bates Aug. 20, 1935 2,204,161Shephard June 11, 1940 2,371,511 Faus Mar. 13, 1945 2,475,684 WeckerlyJuly 12, 1949 2,520,935 Hubbell Sept. 5, 1950 2,522,815 Early Sept. 19,1950 2,577,165 Thorsheim Dec. 4, 1951 FOREIGN PATENTS 476,114 GreatBritain Dec. 2, 1937 553,168 Great Britain May 11, 1943

